FIG. 28 shows a general wire electric discharge machine, and FIG. 29 shows the details of the lower collecting section of a wire electrode disclosed in Japanese Patent Laid-Open No. 63-312025. In FIGS. 28 and 29, numeral 1 is a wire electrode, 2 is a wire bobbin on which the wire electrode 1 is wound, and 3 is a brake roller for tensing the wire electrode 1. Numeral 4 is an auxiliary roller for brake roller 3, 5 is an upper guide roller for changing the direction of the wire electrode 1, and 6 and 7 are upper and lower wire guides, respectively, each having a nozzle for feeding working fluid to a machining gap. Numeral 8 is a workpiece to be machined, 9 is a surface plate for mounting and securing the workpiece 9, and 10 is a lower guide roller which is rotatably supported by a lower arm 12 through a block 11. Numeral 13 is a guide fitting element for guiding the wire electrode 1 to a guide pipe 14, 15 and 16 are pinch rollers for securely feeding the wire electrode 1 to a machining gap, and 17 is a guide plate for changing the direction of the wire electrode 1. The guide plate 17 also serves as a sensor for detecting if the known wire electrode auto feeder is correctly operating. Numeral 18 is a spring for urging an arm 19 downward in order to feed the wire electrode 1. The pinch roller 15 is supported by the arm 19 which is movable by an actuator 20 so as to expand the gap between the pinch rollers 15 and 16 against the pressure of the spring 18. Numeral 21 is a collecting case for collecting the wire electrode 1. Because a voltage pulse is applied between the wire electrode 1 and the workpiece 8 from a power supply (not illustrated), the collecting case 21 is generally made of an insulating material. Numeral 22 is a column of the wire electric discharge machine and numeral 23 is a base for supporting the column 22 and guiding and supporting a saddle 24 which guides and supports a machining bath.
Numeral 30 is a so-called working-fluid feeder for storing the working fluid 28, filtering the sludge produced due to electric discharge machining in the working fluid 28, and adjusting the resistivity of the working fluid 28. Numeral 26 is a working-fluid tank for storing the working fluid 28, and 27 is a pump for feeding the working fluid 28 to the machining bath 25, upper wire guide 6, and lower wire guide 7 through a pipe 29. In general, the working fluid feeder 30 is positioned close to the machine body.
The operation of the wire electric discharge machine shown in FIGS. 28-29 will now be described. The wire electrode 1 is fed from wire bobbin 2 to the collecting case 21 as shown in FIGS. 28-29 under the control of a numerical control unit (not illustrated) during electrical discharge machining. First, the wire electrode 1 from wire bobbin 2 is fed to the upper guide 6 through the brake roller 3, auxiliary roller 4, and upper guide roller 5, and then to the workpiece 8 forming the machining gap to execute electric discharge machining by the pulse voltage sent from a power supply (not illustrated). The used portion of the wire electrode 1 is slightly thinned due to machining, and passes through the lower guide 7, block 11, lower guide roller 10, guide fitting 13, and guide pipe 14 under the control of the numerical control unit, and is wound by the pinch roller 15 and 16 at a commanded speed and collected into the collecting case 21 by the guide plate 17. The wire electrode 1 is curled when it is wound by the pinch rollers 15 and 16 and is collected in collecting case 21 in the form of an approximately uniform circular arc.
Because the conventional wire electric discharge machine has the structure shown in FIGS. 28-29, the curling degree of wire electrode fed and used changes due to the thickness and feed speed of the wire electrode and the erosion rate of the wire thickness changes according to the particular electrical machining conditions. Therefore, with the conventional machine it has not been possible to collect efficiently the used wire electrode because the height of the collected wire electrode locally increases, thereby overflowing from the collecting case 21 even if the case size is increased as shown in FIG. 30.
Other known wire electric discharge machines having collecting devices for collecting a used wire electrode are disclosed in Japanese Kokai's 63-114822 and 63-174820. In Japanese Kokai 63-114822, the collecting device is rotatable.